Electronic device including a trench and a conductive structure therein

ABSTRACT

An electronic device can include a transistor. In an embodiment, the transistor can include a semiconductor layer having a primary surface and a conductive structure. The conductive structure can include a horizontally-oriented doped re-ion lying adjacent to the primary surface, an underlying doped region spaced apart from the primary surface and the horizontally-oriented doped region, and a vertically-oriented conductive region extending through a majority of the thickness of the semiconductor layer and electrically connecting the doped horizontal region and the underlying doped region. In another embodiment, the transistor can include a gate dielectric layer, wherein the field-effect transistor is designed to have a maximum gate voltage of approximately 20 V, a maximum drain voltage of approximately 30 V, and a figure of merit no greater than approximately 30 mΩ*nC. 
     A process of forming an electronic device can include providing a workpiece comprising a substrate, including an underlying doped region, and a semiconductor layer overlying the underlying doped region, wherein the semiconductor layer has a primary surface spaced apart from the underlying doped region. The process can also include forming a vertically-oriented conductive region extending from the primary surface to the underlying doped region, and forming a horizontally-oriented doped region adjacent to the primary surface. In a finished form of the electronic device, the horizontally-oriented doped region extends further in a lateral direction toward a region where a source region has been or will be formed, as compared to the vertically-oriented conductive region. The electronic device includes a transistor that includes the underlying doped region, the vertically-oriented conductive region, and the horizontally-oriented doped region.

RELATED APPLICATION

This application is related to U.S. patent application Ser. No. ______entitled “Process of Forming an Electronic Device Including a Trench anda Conductive Structure Therein” by Loechelt filed of even date (AttorneyDocket No. ONS01173-F2), which is assigned to the current assigneehereof and incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to electronic devices and processes offorming electronic devices, and more particularly to, electronic devicesincluding trenches and conductive structures therein and processes offorming the same.

RELATED ART

Metal-oxide semiconductor field effect transistors (MOSFETs) are acommon type of power switching device. A MOSFET includes a sourceregion, a drain region, a channel region extending between the sourceand drain regions, and a gate structure provided adjacent to the channelregion. The gate structure includes a gate electrode layer disposedadjacent to and separated from the channel region by a thin dielectriclayer.

When a MOSFET is in the on state, a voltage is applied to the gatestructure to form a conduction channel region between the source anddrain regions, which allows current to flow through the device. In theoff state, any voltage applied to the gate structure is sufficiently lowso that a conduction channel does not form, and thus current flow doesnot occur. During the off state, the device must support a high voltagebetween the source and drain regions.

In optimizing the performance of a MOSFET, a designer is often facedwith trade-offs in device parameter performance. Specifically, availabledevice structure or fabrication process choices may improve one deviceparameter, but at the same time such choices may degrade one or moreother device parameters. For example, available structures and processesthat improve on resistance (R_(DSON)) of a MOSFET may reduce thebreakdown voltage (BV_(DSS)) and increase parasitic capacitance betweenregions within the MOSFET.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and are not limited in theaccompanying figures.

FIG. 1 includes an illustration of a cross-sectional view of a portionof a workpiece that includes an underlying doped region, a semiconductorlayer, a pad layer, and a stopping layer.

FIG. 2 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 1 after forming a trench extending through asemiconductor layer to the underlying doped region.

FIG. 3 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 2 after forming a conductive layer thatsubstantially fills the trench.

FIG. 4 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 3 after removing a portion of the conductivelayer lying outside the trench, and after forming a sidewall dopedregion.

FIG. 5 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 4 after removing the stopping layer.

FIG. 6 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 5 after forming a plurality of layers over thesemiconductor layer.

FIG. 7 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 6 after forming a surface doped region and anopening extending through the plurality of layers.

FIG. 8 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 7 after forming an insulating sidewall spacer.

FIG. 9 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 8 after forming a conductive layer over Weexposed surface of the workpiece, and forming a well region within thesemiconductor layer.

FIG. 10 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 9 after forming a remaining portion of theconductive layer over the exposed surface of the workpiece.

FIG. 11 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 10 after forming a gate electrode.

FIG. 12 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 11 after removing an uppermost insulatinglayer, truncating the insulating sidewall spacer, and filling a gapbetween the gate electrode and the conductive layer with a conductivefill material.

FIG. 13 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 12 after forming an opening through interleveldielectric layer and the source region, and after forming a well contactregion.

FIG. 14 includes an illustration of a cross-sectional view of a portionof the workpiece of FIG. 13 after forming a substantially completedelectronic device in accordance with an embodiment of the presentinvention.

FIGS. 15 to 17 include illustrations of cross-sectional views of aportion of the workpiece of FIG. 1 wherein a conductive structure isformed within the trench, wherein the conductive structure includes anelevated portion that overlies a primary surface of the semiconductorsubstrate.

FIG. 18 includes an illustration of a cross-sectional view of a portionof a workpiece in which the electronic device includes a powertransistor having a compensation region lying beneath ahorizontally-oriented doped region.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of embodiments of the invention.

DETAILED DESCRIPTION

The following description in combination with the figures is provided toassist in understanding the teachings disclosed herein. The followingdiscussion will focus on specific implementations and embodiments of theteachings. This focus is provided to assist in describing the teachingsand should not be interpreted as a limitation on the scope orapplicability of the teachings. However, other teachings can certainlybe utilized in this application.

As used herein, the terms “horizontally-oriented” and“vertically-oriented,” with respect to a region or structure, refers tothe principal direction in which current flows through such region orstructure. More specifically, current can flow through a region orstructure in a vertical direction, a horizontal direction, or acombination of vertical and horizontal directions. If current flowsthrough a region or structure in a vertical direction or in acombination of directions, wherein the vertical component is greaterthan the horizontal component such a region or structure will bereferred to as vertically oriented. Similarly, if current flows througha region or structure in a horizontal direction or in a combination ofdirections, wherein the horizontal component is greater than thevertical component, such a region or structure will be referred to ashorizontally oriented.

The term “normal operation” and “normal operating state” refer toconditions under which an electronic component or device is designed tooperate. The conditions may be obtained from a data sheet or otherinformation regarding voltages, currents, capacitance, resistance, orother electrical conditions. Thus, normal operation does not includeoperating an electrical component or device well beyond its designlimits.

The terms “comprises,” “comprising,” “includes,” “including,” “has,”“having” or any other variation thereof, are intended to cover anon-exclusive inclusion. For example, a method, article, or apparatusthat comprises a list of features is not necessarily limited only tothose features but may include other features not expressly listed orinherent to such method, article, or apparatus. Further, unlessexpressly stated to the contrary, “or” refers to an inclusive-or and notto an exclusive-or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or notpresent), A is false (or not present) and B is true (or present), andboth A and B are true (or present).

Also, the use of “a” or “an” is employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural, or vice versa, unless it is clear that it is meantotherwise. For example, when a single item is described herein, morethan one item may be used in place of a single item. Similarly, wheremore than one item is described herein, a single item may be substitutedfor that more than one item.

Group numbers corresponding to columns within the Periodic Table of theelements use the “New Notation” convention as seen in the CRC Handbookof Chemistry and Physics, 81^(st) Edition (2000-2001).

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. The materials, methods, andexamples are illustrative only and not intended to be limiting To theextent not described herein, many details regarding specific materialsand processing acts are conventional and may be found in textbooks andother sources within the semiconductor and electronic arts.

FIG. 1 includes an illustration of a cross-sectional view of a portionof a workpiece 100. The workpiece 100 includes an underlying dopedregion 102 that is lightly doped or heavily doped, n-type or p-type. Forthe purposes of this specification, heavily doped is intended to mean apeak dopant concentration of at least 10¹⁹ atoms/cm³, and lightly dopedis intended to mean a peak dopant concentration of less than 10¹⁹atoms/cm³. The underlying doped region 102 cm be a portion of a heavilydoped substrate (e.g., a heavily n-type doped wafer) or may be a burieddoped region overlying a substrate of opposite conductivity type oroverlying a buried insulating layer (not illustrated) that lies betweena substrate and the buried doped region. In a particular embodiment, theunderlying doped region 102 can include a lightly doped portionoverlying a heavily doped portion, for example when an overlyingsemiconductor layer 104 has an opposite conductivity type, to helpincrease the junction breakdown voltage. In an embodiment, theunderlying doped region 102 is heavily doped with an n-type dopant, suchas phosphorus, arsenic, antimony, or any combination thereof. In aparticular embodiment, the underlying doped region 102 includes arsenicor antimony if diffusion of the underlying doped region 102 is to bekept low, and in a particular embodiment, the underlying doped region102 includes antimony to reduce the level of outgassing (as compared toarsenic) during formation of the semiconductor layer 104.

In the embodiment illustrated in FIG. 1, the semiconductor layer 104overlies the underlying doped region 102. The semiconductor layer 104has a primary surface 105. The semiconductor layer 104 can include aGroup 14 element (i.e., carbon, silicon, germanium or any combinationthereof) and any of the dopants as described with respect to theunderlying doped region 102 or dopants of the opposite conductivitytype. In an embodiment, the semiconductor layer 104 is a lightly dopedn-type or p-type epitaxial silicon layer having a thickness in a rangeof approximately 0.5 microns to approximately 5.0 microns, and a dopingconcentration no greater than approximately 10¹⁶ atoms/cm³, and inanother embodiment, a doping concentration of least approximately 10¹⁴atoms/cm³.

A pad layer 106 and a stopping layer 108 (e.g., a polish-stop layer oran etch-stop layer) are formed over he semiconductor layer 104 using athermal growth technique, a deposition technique, or a combinationthereof. Each of the pad layer 106 and the stopping layer 108 caninclude an oxide, a nitride, an oxynitride, or any combination thereof.In an embodiment the pad layer 106 has a different composition ascompared to the stopping layer 108. In a particular embodiment, the padlayer 106 includes an oxide, and the stopping layer 108 includes anitride.

Referring to FIG. 2, portions of the semiconductor layer 104, pad layer106, and stopping layer 108 are removed to form trenches, such as trench202, that extend from the primary surface 105 toward the underlyingdoped region 102. The trench 202 may be a single trench with differentparts illustrated in FIG. 2, or the trench 202 can include a pluralityof different trenches. The width of the trench 202 is not so wide that asubsequently-formed conductive layer is incapable of filling the trench202. In a particular embodiment, the width of each trench 202 is atleast approximately 0.3 micron or approximately 0.5 micron, and inanother particular embodiment, the width of each trench 202 is nogreater than approximately 4 microns or approximately 2 microns. Afterreading this specification, skilled artisans will appreciate thatnarrower or wider widths outside the particular dimensions described maybe used. The trenches 202 can extend to the underlying doped region 102;however, the trenches 202 may be shallower if needed or desired.

The trenches are formed using an anisotropic etch. In an embodiment, atimed etch can be performed, and in another embodiment, a combination ofendpoint detection (e.g., detecting the dopant species from theunderlying doped region 102, such as arsenic or antimony) and a timedoveretch may be used.

If needed or desired, a dopant can be introduced into a portion of thesemiconductor layer 104 along a sidewall 204 of the trench 202 to form asidewall doped region (not illustrated in FIG. 2) that is heavily doped.A tilt angle implant technique, a dopant gas, or a solid doping sourcemay be used.

A conductive layer 302 is formed over the stopping layer 108 and withinthe trench 202, as illustrated in FIG. 3. The conductive layer 302substantially fills the trench 202. The conductive layer 302 can includea metal-containing or semiconductor-containing material. In anembodiment, the conductive layer 302 can include a heavily dopedsemiconductor material, such as, amorphous silicon or polysilicon. Inanother embodiment, the conductive layer 302 includes a plurality offilms, such as an adhesion film a brier film, and a conductive fillmaterial. In a particular embodiment, the adhesion film can include arefractory metal, such as titanium, tantalum, or the like; the barrierfilm can include a refractory metal nitride, such as titanium nitride,tantalum nitride, or the like, or a refractorymetal-semiconductor-nitride, such as TaSiN; and the conductive fillmaterial can include tungsten. In a more particular embodiment, theconductive layer 302 can include Ti/TiN/W. The selection of the numberof films and composition(s) of those film(s) depend on electricalperformance, the temperature of a subsequent heat cycle, anothercriterion, or any combination thereof. Refractory metals and refractorymetal-containing compounds can withstand high temperatures (e.g.,melting points of such materials can be at least 1400° C.), may beconformally deposited, and have a lower bulk resistivity than heavilydoped n-type silicon. After reading this specification, skilled artisanswill be able to determine the composition of the conductive layer 302 tomeet their needs or desires for a particular application.

A portion of the conductive layer 302 that overlies the stopping layer108 is removed to form conductive structures within the trenches, suchas conductive structure 402 within the trench 202, as illustrated in theembodiment of FIG. 4. The removal can be performed using achemical-mechanical polishing or blanket etching technique. The stoppinglayer 108 may be used as a polish-stop or etch-stop layer. Polishing oretching may be continued for a relatively short time after the stoppinglayer 108 is reached to account for a non-uniformity across theworkpiece with respect to the thickness of the conductive layer 302, thepolishing or etching operation, or any combination thereof.

Before, during, or after formation of the conductive structures,sidewall doped regions, such as sidewall doped region 404, can be formedfrom portions of the semiconductor layer 104 and extend from thesidewall 204. The dopant may be introduced during a doping operationpreviously described and become activated when the conductive layer 302is formed. Alternatively, when the conductive layer 302 includes a dopedsemiconductor material, dopant may diffuse from the conductive structure402 or from the conductive layer 302 (before formation of the conductivestructure 402 is completed). The conductive structure 402 and thesidewall doped region 404, if present, form a vertically-orientedconductive region. When in the form of a finished electronic device, theprincipal charge carrier (e.g., electron) or current flow through theconductive structure 402 is principally in a vertical direction(substantially perpendicular to the primary surface 105), as opposed toa horizontal direction (substantially parallel to the primary surface105).

In FIG. 5, the stopping layer 108 is removed, and portions of thesemiconductor layer 104 lying immediately adjacent to the primarysurface 105 and the sidewall doped regions, such as sidewall dopedregion 404, are doped to form horizontally-oriented doped regions, suchas surface doped region 504, that are spaced apart from the underlyingdoped region 102. The surface doped region 504 has the same conductivitytype as the sidewall doped region 404 and the underlying doped region102. In a normal operating state, the principal charge carrier(electron) or current flow through the surface doped region 504 will bein horizontal direction. Thus, the surface doped region 504 can be ahorizontally-oriented doped region. The surface doped region 504 has adepth in a range of approximately 0.1 micron to approximately 0.5microns, and extends from the sidewall doped region 404 of thevertically-oriented conductive structure in a range of approximately 0.2micron to approximately 2.0 microns. The lateral dimension (from thevertically-oriented conductive structure) can depend on the voltagedifference between the source and drain of the power transistor beingformed. As the voltage difference between the source and drain of thetransistor increases, the lateral dimension can also increase. In anembodiment, the voltage difference is no greater than approximately 30V, and in another embodiment, the voltage difference is no greater than20 V. The peak doping concentration within the horizontally-orienteddoped region can be in a range of approximately 2×10¹⁷ atoms/cm³ toapproximately 2×10¹⁸ atoms/cm³, and in a particular embodiment, in arange of approximately 4×10¹⁷ atoms/cm³ to approximately 7×10¹⁷atoms/cm³. The pad layer 106 remains over the semiconductor layer 104after formation of the surface doped regions 504, or is removed afterthe surface doped regions 504 are formed.

A set of layers are formed over the semiconductor layer 104 and theconductive structure 402 in FIG. 6. In an embodiment, an insulatinglayer 602, a conductive layer 604, an insulating layer 606, aninsulating layer 622, a conductive layer 624, and an insulating layer626 cm be serially deposited. Each of the insulating layers 602, 606,622, and 626 can include an oxide, a nitride, an oxynitride, or mycombination thereof.

Each of the conductive layers 604 and 624 include a conductive materialor may be made conductive, for example, by doping. Each of theconductive layers 604 and 624 can include a doped semiconductor material(e.g., heavily doped amorphous silicon, polysilicon, etc.), ametal-containing material (a refractory metal, a refractory metalnitride, a refractory metal silicide, etc.), or any combination thereof.The conductive layer 604 has a thickness in a range of approximately0.05 to 0.5 microns, and the conductive layer 624 can have a thicknessin a range of approximately 0.1 to 0.9 microns. In a particularembodiment, the conductive layer 604 is a conductive electrode layerthat will be used to form a conductive electrode, and the conductivelayer 624 is a gate signal layer. The significance of such layers willbe described later in this specification. The conductive layer 624 maybe etched or otherwise patterned at his time to form a gate signal lineor may be etched or otherwise patterned at a later point in the processflow. Similarly, the conductive layer 604 may be etched or otherwisepatterned at this time to form a conductive electrode or may bepatterned at a later point in the process flow.

In another particular embodiment, the insulating layers 602 and 606include a nitride each having a thickness in a range of approximately0.05 microns to approximately 0.2 microns. The insulating layers 622 and626 include an oxide, the insulating layer 622 can have a thickness in arange of approximately 0.2 microns to approximately 0.9 microns, and theinsulating layer 626 can have a thickness in a range of approximately0.05 microns to approximately 0.2 microns. An antireflective layer maybe incorporated within any of the insulating or conductive layers or maybe used separately (not illustrated). In another embodiment, more orfewer layers may be used, and thicknesses as described herein are merelyillustrative and not meant to limit the scope of the present invention.

Openings, such as opening 702, are formed through the layers 602, 604,606, 622, 624, and 626, as illustrated in FIG. 7. The openings areformed such that portions of the surface doped region 504 underlie theopening 702. Such portions allow part of the surface doped region 504 tounderlie part of a subsequently-formed gate electrode. Insulatingspacers, such as insulating spacer 802, are formed along sides of theopenings, such as opening 702 in FIG. 8. The insulating spacerselectrically insulate the conductive layer 604 from asubsequently-formed gate electrode. The insulating spacer 802 caninclude an oxide, a nitride, an oxynitride, or any combination thereof,and has a width at the base of the insulating spacer 802 in a range ofapproximately 50 nm to approximately 200 nm.

FIG. 9 includes an illustration of the workpiece after forming a gatedielectric layer 902, a conductive layer 906, and a well region 904. Thepad layer 106 is removed by etching and the gate dielectric layer 902 isformed over the semiconductor layer 104. In a particular embodiment, thegate dielectric layer 902 includes an oxide, a nitride, an oxynitride,or any combination thereof and has a thickness in a range ofapproximately 5 nm to approximately 100 nm, and the conductive layer 906overlie the gate dielectric layer 902. The conductive layer 906 can bepart of subsequently-formed gate electrodes. The conductive layer 906can be conductive as deposited or can be deposited as a highly resistivelayer (e.g., undoped polysilicon) and subsequently made conductive. Theconductive layer 906 can include a metal-containing orsemiconductor-containing material. The thickness of the conductive layer906 is selected such that, from a top view, a substantially verticaledge of the conductive layer 906 exposed within the opening 702 is nearthe edge of the surface doped region 504. In an embodiment, theconductive layer 906 is deposited to a thickness of about 0.1 microns toabout 0.15 microns.

After the conductive layer 906 is formed, the semiconductor layer 104can be doped to form well regions, such as well region 904 in FIG. 9.The conductivity type of the well region 904 is opposite that of thesurface doped region 504 and underlying doped region 102. In anembodiment, boron dopant is introduced through opening 702, theconductive layer 906, and the gate dielectric layer 902 intosemiconductor layer 104 to provide p-type dopant for the well region904. In one embodiment, the well region 904 has a depth greater than adepth of a subsequently-formed source region, and in another embodiment,the well region 904 has a depth of at least approximately 0.5 microns.In a further embodiment, the well region 904 has a depth no greater thanapproximately 2.0 microns, and in still another embodiment, no greaterthan approximately 1.5 microns. By way of example, the well region 904can be formed using two or more ion implantations. In a particularexample, each ion implantation is performed using a dose ofapproximately 1.0×10¹³ atoms/cm², and the two implants having energiesof about 25 KeV and 50 KeV. In another embodiment, more or fewer ionimplantations may be performed in forming the well regions. Differentdoses may be used at the different energies, higher or lighter doses,higher or lower energies, or any combination thereof may be used to meetthe needs or desires for a particular application.

Additional conductive material is deposited on the conductive layer 906to form the conductive layer 1006, as illustrated in FIG. 10. Gateelectrodes will be formed from the conductive layer 1006, and therefore,he conductive layer is a gate electrode layer in the illustratedembodiment. The conductive layer 1006 can include any of the materialspreviously described with respect to the conductive layer 906. Similarto the conductive layer 906, the additional conductive material can beconductive as deposited or can be deposited as a highly resistive layer(e.g., undoped polysilicon) and subsequently made conductive. As betweenthe conductive layer 906 and additional conductive material, they canhave the same composition or different compositions. The thickness ofthe conductive layer 1006, including the conductive layer 906 and theadditional conductive material, has a thickness in a range ofapproximately 0.2 microns to approximately 0.5 microns. In a particularembodiment, the additional conductive material includes polysilicon andcan be doped with an n-type dopant during deposition or dopedsubsequently using ion implantation or another doping technique.

The conductive layer 1006 is anisotropically etched to form gateelectrodes, such as gate electrode 1106 in FIG. 11. In the illustratedembodiment, the gate electrode 1106 is formed without using a mask andhas a shape of a sidewall spacer. The etch to perform the gate electrode1106 can be performed such that he insulating layer 626 and gatedielectric layer 902 are exposed. The etch can be extended to expose aportion of the insulating sidewall spacer 802. In the embodiment asillustrated in FIG. 11, a portion of the conductive electrode 604 liesadjacent to the gate electrode 1106, wherein the insulating sidewallspacer 802 lies between the conductive electrode 604 and the gateelectrode 1106. The conductive electrode 604 has a pair of opposingsurfaces, one of which is closer to the primary surface 105, and theother opposing surface is farther from the primary surface 105. Withinan area occupied by the transistor, each of the opposing surfaces of theconductive electrode 604 lies at elevations between lowermost anduppermost points of the gate electrode 1106. An insulating layer (notillustrated) may be thermally grown from the gate electrode 1106 or maybe deposited over the workpiece. The thickness of the insulating layercan he in a range of approximately 10 nm to approximately 30 nm.

FIG. 12 includes an illustration of the workpiece after forming aconductive electrode 1262, a gate signal line 1264, a truncatedinsulating sidewall spacer 1202, a source region 1204, and a conductivefill material 1206 between the gate signal line 1264 and the gateelectrode 1106. Although the operations carried out to form theworkpiece are described in a particular order, after reading thisspecification, skilled artisans will appreciate that the order can bechanged as needed or desired. In addition, a mask or a plurality ofmasks (not illustrated) may be used to achieve the workpiece in theembodiment illustrated in FIG. 12.

If the conductive layers 604 and 624 have not yet been patterned, theyare patterned to form conductive electrodes and gate signal lines, suchas conductive electrode 1262 and gate signal line 1264. The conductiveelectrode 1262 can be used to help reduce capacitive coupling betweenthe vertically-oriented conductive region (combination of conductivestructure 402 and sidewall doped region 404) and any one or more of thegate signal line 1264, the gate electrode 1106, or both the gate signalline 1264 and the gate electrode 1106. The gate signal line 1264 can beused to provide signals from control electronics (not illustrated) tothe gate electrode 1106. Within an area occupied by the transistor, thegate signal line 1264 overlies the conductive electrode 1262. In anembodiment, within the transistor, the gate signal line 1264 overliessubstantially all of the conductive electrode 1262, and in anotherembodiment, within the transistor, the gate signal line 1264 overliesonly a part and not all of the conductive electrode 1262.

Source regions, such as source region 1204, can be formed using ionimplantation. The source region 1204 is heavily doped and has anopposite conductivity type as compared to the well region 904 and thesame conductivity type as the surface doped region 504 and theunderlying doped region 102. The portion of the well region 904 lyingbetween the source region 1204 and the surface doped region 504 andunderlying the gate electrode 1106 is a channel region 1222 for thepower transistor being formed.

The insulating sidewall spacer 802 can be truncated to form thetruncated insulating sidewall spacer 1202 by etching an upper portion ofthe sidewall spacer 802 to remove part of the insulating sidewall spacer802 from between the conductive layer 624 (gate signal layer) and thegate electrode 1106. The amount of the insulating spacer 802 that isremoved is at least enough to allow the conductive fill material 1206,when formed, to electrically connect the conductive layer 624 and thegate electrode 1106 but not etching so much of the insulating sidewallspacers 802 to expose the conductive layer 604 (the conductive electrodelayer) as the gate electrode 1106 and conductive layer 624 would beelectrically connected to the conductive layer 604, which is undesired.In the embodiment as illustrated, the etching is performed such that anuppermost surface of the truncated insulating sidewall spacer 1202 liesat about the interface between the insulating layer 622 and theconductive layer 624.

The conductive fill material 1206 is formed above the truncatedinsulating spacer 1202 to electrically connect the gate electrode 1106to the conductive layer 624. The conductive fill material 1206 may beselectively grown or deposited over substantially all of the workpieceand subsequently removed from regions outside the gap between the gateelectrode 1106 and the gate signal line 1264. Exposed portions of theinsulating layer 626 and gate dielectric layer 902 are removed, ifneeded or desired.

FIG. 13 includes an illustration of the workpiece after an interleveldielectric (ILD) layer 1302 has been formed and patterned to definecontact openings, and after doping to form well contact regions. The ILDlayer 1302 can include an oxide, a nitride, an oxynitride, or anycombination thereof. The ILD layer 1302 can include a single film havinga substantially constant or changing composition (e.g., a highphosphorus content further from the semiconductor layer 104) or aplurality of discrete films. An etch-stop layer, an antireflectivelayer, or a combination may be used within or over the ILD layer 1302 tohelp with processing. The ILD layer 1302 may be planarized to improveprocess margin during subsequent processing operations (e.g.,lithography, subsequent polishing, or the like). A resist layer 1304 isformed over the ILD layer 1302 and is patterned to define resist layeropenings. An anisotropic etch is performed to define contact openings,such as the contact opening 1322, that extend through the ILD layer1302. Unlike many conventional contact etch operations, the etch iscontinued to extend through the source region 1204 and ends within thewell region 904. The etch can be performed as a timed etch or as anendpoint detected etch with a timed overetch The firs t endpoint may bedetected when the source region 1204 becomes exposed, and a secondendpoint may be detected by the presence of boron within the well region904 in a particular embodiment. Well contact regions, such as e wellcontact region 1324, are formed by doping the bottom part of the contactopenings, such as the contact opening 1322. The well contact region 1324may be implanted with a dopant having the same conductivity type as thewell region 904 in which it resides. The well contact region 1324 isheavily doped so that an ohmic contact can be subsequently formed. Whilethe resist layer 1304 is in place, an isotropic etch can be performed toexpose uppermost surfaces of the source regions, such as the sourceregion 1204, as will become more apparent with the description withrespect to FIG. 14. At this point in the process, the power transistors,such as the power transistor as illustrated in FIG. 13, are formed.

FIG. 14 includes an illustration of a substantially completed electronicdevice that includes conductive plugs and terminals. More particularly,a conductive layer is formed along the exposed surface of the workpieceand within the contact openings, including the contact opening 1322. Theconductive layer can include a single film or a plurality of films. Inan embodiment, the conductive layer includes a plurality of films, suchas an adhesion film, a barrier film, and a conductive fill material. Ina particular embodiment, the adhesion film can include a refractorymetal, such as titanium, tantalum, or the like; the barrier film caninclude a refractory metal nitride, such as titanium nitride, tantalumnitride, or the like, or a refractory metal-semiconductor-nitride, suchas TaSiN, and the conductive fill material can include tungsten. Theselection of the number of films and composition(s) of those film(s)depend on electrical performance, the temperature of a subsequent heatcycle, another criterion, or any combination thereof. Refractory metalsand refractory metal-containing compounds can withstand hightemperatures (e.g., melting points of such materials can be at least1400° C.). After reading tis specification, skilled artisans will beable to determine the composition of the conductive layer to meet theirneeds or desires for a particular application. The portion of theconductive layer hat overlies the insulating layer 1302 is removed toform conductive plugs, such as the conductive plug 1422 within thecontact opening 1322.

Conductive layers can be deposited to form a source terminal 1424 and adrain terminal 1426. The conductive layers may each include a singlefilm or a plurality of discrete film. Exemplary materials includealuminum, tungsten, copper, gold, or the like. Each conductive layer mayor may not be patterned to form the source terminal 1424, or the drainterminal 1426, as illustrated in FIG. 14. In a particular embodiment,the drain terminal 1426 may be part of a backside contact to thesubstrate that includes the underlying doped region 102. In anotherembodiment, the conductive layer that is used to form the sourceterminal 1424 may be patterned to also form a gate terminal (notillustrated) that would be coupled to the gate signal line 1264. In theembodiment as illustrated, no conductive plugs extend to thevertically-oriented conductive regions, and particularly to theconductive structure 402.

The electronic device can include many other power transistors that aresubstantially identical to the power transistor as illustrated in FIG.14. The power transistors are connected in parallel to give a sufficienteffective channel width of the electronic device that can support therelatively high current flow that is used during normal operation of theelectronic device. In a particular embodiment, the electronic device maybe designed to have a maximum source-to-drain voltage difference of 30V, and a maximum source-to-gate voltage difference of 20 V. Duringnormal operation, the source-to-drain voltage difference is no greaterthan approximately 20 V, and the source-to-gate voltage difference is nogreater than approximately 9 V. The conductive electrode 1262 can bekept at a substantially constant voltage during operation to reduce thedrain-to-gate capacitance. In a particular embodiment, the conductiveelectrode 1262 may be at substantially 0 V, in which case, theconductive electrode 1262 can act as a grounding plane. In anotherembodiment, the conductive electrode 1262 may be coupled to the sourceterminal 1424.

The electronic device can be used in an application where the switchingspeed of the power transistor needs to be relatively high. For example,a conventional electronic device may only be capable of a switchingspeed of 0.35 MHz. An embodiment as described herein can be used withsimilar voltages and current flows and achieve a switching speed of atleast approximately 2 MHz, and in a particular embodiment, can achieve aswitching speed of at least 10 MHz, 20 MHz, or potentially higher. Anon-limiting application can include the electronic device used as partof a voltage regulator within a computer, such as a personal computer.

Such performance may be achieved by forming an electronic device with alow level of parasitic characteristics. The resistance through theelectronic device (R_(DSON)) can be kept to a sufficiently low amountwhile the parasitic capacitance within the power transistor is keptrelatively low. When the power transistor has a maximum source-to-gatevoltage difference of 20 V and a maximum source-to-drain voltage of 30V, the electronic device can have a figure of merit of no greater Canapproximately 30 mΩ*nC, and in a particular embodiment, no greater than20 mΩ*nC. The figure of merit is a product of the on resistance(R_(DSON)) times the total gate charge required to switch a device froma substantially fully off or voltage blocking state to an on or currentconducting state (Q_(TOTAL)). Conventional electronic devices havehigher values for the figure of merit. For example, a conventionalelectronic device with trench power MOSFETs can have a figure of meritof greater than 70 mΩ*nC, and another conventional device similar tothat described in U.S. Pat. No. 7,397,084 can have a figure of merit ofat least 50 mΩ*nC (both figure of merit numbers are with respect to amaximum source-to-gate voltage difference of 20 V and a maximumsource-to-drain voltage of 30 V).

Although meant to limit the invention, part of the improved performancemay be related to using the surface doped region 504 (e.g., ahorizontally-oriented doped region) and the vertically-orientedconductive region (conductive plug 402 with or without the sidewalldoped region 404). A combination of the surface doped region 504, thevertically-oriented conductive region, and the underlying doped region102 form a conductive structure that has relatively lower parasiticcharacteristics. FIG. 14 includes arrows 1442 that illustrate theprincipal charge carrier (e.g., electron or hole) flow through theelectronic device, and more particularly, the power transistor.Electrons from the source terminal 1424 pass through the conductive plug1422 and enter the source region 1204. When the power transistor is on,electrons flow through the channel region of THE power transistor(portion of the well region 904 between the source region 1204 and thesurface doped region 504) and ten into the surface doped region 504.Within the surface doped region 504, the electrons flow in more of ahorizontal direction, as opposed to a vertical direction, and therefore,the electrons (and current) principally flow in the horizontaldirection. The electrons flow from the surface doped region 504 into thevertically-oriented conductive region, and particularly the conductivestructure 402. Within the vertically-oriented conductive region, theelectrons flow in more of a vertical direction, as opposed to ahorizontal direction, and therefore, the electrons (and current)principally flow in the vertical direction.

Because most of the electrons (current) are not flowing verticallythrough substantially all of the thickness of the semiconductor layer104, itself, the doping concentration of the semiconductor layer 104 canbe reduced without significantly adversely affecting R_(DSON). Therelatively lower concentration of the semiconductor layer 104 helps toreduce parasitic capacitive coupling.

Other embodiments can be used if needed or desired. In a particularembodiment, the capacitive coupling between the vertically-orientedconductive region and the gate electrode may be further reduced. In FIG.15, a portion of a workpiece 1500 is illustrated having layers 102, 104,106, and 108 as previously described In a particular embodiment, the padlayer 106, the stopping layer 108, or both may be thicker than thecorresponding layers within the workpiece 100 of FIG. 1. The workpiecealso includes the trench 202 and sidewall 204 as previously described.Unlike workpiece 100, the workpiece 1500 includes portion 1502 in whichportions of the pad layer 106 have been removed under the stopping layer108 to expose part of the primary surface 105 of the semiconductor layer104. The structure as illustrated in FIG. 15 can be achieved byperforming an isotropic etch (wet or dry) of the pad layer 106, whereinthe chemistry for the isotropic etch is selective to the other materialsof the workpiece 1500 that are exposed at the time of the isotropicetch. In a particular embodiment, the underlying doped region 102 andthe semiconductor layer 104 includes a monocrystalline semiconductormaterial, the pad layer includes an oxide, and the stopping layer 108includes a nitride. An HF solution can be used to etch the pad layer 106to produce the undercut as illustrated.

In FIG. 16, the conductive structure 1602 and doped region 1604 can beformed in a manner similar to the conductive structure 402 and sidewalldoped region 404. The material for the conductive structure 402 can beconformally deposited so that the gap formed by removing part of the padlayer 106 is substantially filled. In a particular embodiment, anamorphous or a polycrystalline silicon layer is conformally deposited.Unlike the conductive structure 402, an elevated portion 1606 of theconductive structure 1602 overlies the primary surface 105 of thesemiconductor layer 104 at portions 1502. Unlike the sidewall dopedregion 404, the doped region 160 is formed within the portions 1502. Theelevated portion 1606 of the conductive structure 1602 that overlies theprimary surface 105 has a height that generally corresponds to thecombined thickness of the layers 106 and 108. In another embodiment (notillustrated), the pad layer 106 and stopping layer 108 can be patterned,so that both are removed. In other words, the portions of the stoppinglayer 108 that overlie the portions 1502 are also removed. In thisparticular embodiment, the deposition of material for the conductivestructure 1602 may be less conformal that the deposition used for theembodiment as illustrated in FIG. 16.

FIG. 17 includes an illustration of the workpiece 1500 after additionalprocessing to a point in the process similar to a previously describedembodiment as illustrated in FIG. 12. The table below lists features asillustrated in FIG. 17 and the corresponding features in FIG. 12. Eachof the features in FIG. 17 can have any of the materials, thicknesses,and be formed using any of the methods as previously described withrespect to its corresponding feature illustrated in FIG. 12. Forexample, the gate dielectric layer 1702 can include any of thematerials, thicknesses, and be formed using any of the methods aspreviously described with respect to the gate dielectric layer 902.

TABLE FIG. 17 FIG. 12 Gate dielectric layer 1702 Gate dielectric layer902 Horizontally-oriented doped region 1704 Surface doped region 504Well region 1714 Well region 904 Channel region 1722 Channel region 1222Source region 1724 Source region 1204 Insulating layer 1732 Insulatinglayer 602 Insulating layer 1736 Insulating layer 606 Insulating layer1752 Insulating layer 622 Conductive electrode 1762 Conductive electrode1262 Gate signal line 1764 Gate signal line 1264 Gate electrode 1786Gate electrode 1106 Conductive fill material 1796 Conductive fillmaterial 1206

The shapes of some of the features in FIG. 17 are different from hecorresponding features in FIG. 12 due to the different shape of theconductive structure 1602 as compared to the conductive structure 402.Thus, horizontally-oriented doped region 1704 does not extend to thetrench, and the insulating layers 1732, 1736, 1752, the conductiveelectrode 1762, and the gate signal line 1764 change elevations betweena region above the conductive structure 1602 and another region closerto the gate electrode 1786. The change in elevations may reducecapacitive coupling between the gate electrode 1786 and the conductivestructure 1602 as compared to the capacitive coupling between the ateelectrode 1106 and the conductive structure 402 in the embodiment asillustrated in FIG. 12. Furthermore, the elevated portion 1606 enablesthe vertical portion (main portion) of the conductive structure 1602 tobe placed farther from well region 1714 without significantly increasingthe R_(DSON). This greater spacing has the beneficial effect ofincreasing the breakdown voltage of the device. In a particularembodiment, an uppermost surface of the elevated portion 1606 of theconductive structure 1602 lies at an elevation higher than a lowermostsurface of the gate electrode 1786 (e.g., the base of the sidewallspacer structure of the gate electrode 1786).

In another embodiment, a compensation region may be used to help lowerR_(DSON). In an embodiment as illustrated in FIG. 18, a compensationregion 1804 may be used adjacent to the surface doped region 504. Duringnormal operating conditions, the surface doped region 504 can besimultaneously depleted from above by the conductive electrode 1262 andfrom below by the compensating region 1804. This can allow the peakdopant concentration in the surface doped region 504 to be increased andresult in a lower R_(DSON) for the same breakdown voltage (BV_(DSS))rating.

The compensation region 1804 has a conductivity type opposite that ofthe surface doped region 504 and the underlying doped region 102. Thecompensation region 1804 has a dopant concentration no greater tanapproximately 2×10¹⁷ atoms/cm³ in a particular embodiment, or no greaterman approximately 5×10¹⁶ atoms/cm³ in another particular embodiment. Thecompensation region 1804 has a depth (as measured from the primarysurface 105 of the semiconductor layer 104, see FIG. 1) that is greaterthan the depth of the surface doped region 504, and in anotherembodiment, the portion of the semiconductor layer 104 that is not partof a different doped region (e.g., the surface doped region 504, wellregion 904, sidewall doped region 404, etc.) can be the compensationregion. In a particular embodiment, the compensation region 180 has adepth that is within approximately 0.5 micron of the depth of the wellregion 904. The compensation region 1804 can be formed by doping thesemiconductor layer 104 during substantially all or a later portion ofan epitaxial deposition. In another embodiment, the compensation region1804 can be formed using a relatively higher energy implant than animplant used in forming the surface doped region 504. After reading hisspecification, one of ordinary skill in the art will be able to selectthe energy or energies (if more than one implant is used to form thecompensation region 1804) for the implant(s), based on the depth andconcentration profile that is needed or desired for the compensationregion 1804.

In still another embodiment (not illustrated), the insulating layer 602can be terraced. More particularly, the insulating layer can be thinnerat a location closer to the gate electrode 1106 as compared to alocation over the conductive structure 402. The terracing of theinsulating layer 602 may he more useful as V_(D) increases. Therelatively thinner portion of the insulating layer 602 allows the gateelectrode 1106 to be less capacitively coupled to the drain, and therelatively thicker portion of the insulating layer 602 reduces thelikelihood of a dielectric breakdown between the conductive structure402 and the conductive electrode 1262.

The transistor as illustrated and described herein can be an NMOStransistor, in which the source region 1204, surface doped region 504,sidewall doped region 404, and underlying doped region 102 are n-typedoped, and the channel region 1222 is p-type doped. In this particularembodiment, the charge carriers are electrons, and current flows in adirection opposite that of the electrons. In another embodiment, thetransistor can be a PMOS transistor by reversing the conductivity typesof the previously described regions. In this particular embodiment, thecharge carriers are holes, and current flows in the same direction asthe holes.

Many different aspects and embodiments are possible. Some of thoseaspects and embodiments are described below. After reading thisspecification, skilled artisans will appreciate that those aspects andembodiments are only illustrative and do not limit the scope of thepresent invention.

In a first aspect, an electronic device can include a transistor,wherein the transistor can include a semiconductor layer having aprimary surface and a conductive structure. The conductive structure caninclude a horizontally-oriented doped region lying adjacent to theprimary surface, an underlying doped region spaced apart from theprimary surface and the horizontally-oriented doped region and avertically-oriented conductive region extending through a majority ofthe thickness of the semiconductor layer and electrically connecting thedoped horizontal region and the underlying doped region. The electronicdevice can further include a conductive electrode overlying andelectrically insulated from the conductive structure, wherein theconductive electrode is configured to be at a substantially constantvoltage when the electronic device is in a normal operating state. Theelectronic device can still further include a gate electrode overlyingthe primary surface of the semiconductor layer, and a gate signal lineoverlying the primary surface of the semiconductor layer and theconductive structure, wherein within an area occupied by the transistor,the gate signal line overlies the conductive electrode.

In an embodiment of the first aspect, the vertically-oriented conductiveregion includes an elevated portion that overlies the primary surface ofthe semiconductor layer. In a particular embodiment, the elevatedportion has an uppermost surface that lies at an elevation higher than alowermost surface of the gate electrode. In another embodiment, thesemiconductor layer includes a compensating region, the compensatingregion lies between the horizontally-oriented doped region and theunderlying doped region and extends substantially to thevertically-oriented conductive region, and the compensating region hasconductivity type opposite that of the horizontally-oriented dopedregion and the underlying doped region. In still another embodiment, thevertically-oriented conductive structure includes a conductive plug. Ina particular embodiment, the conductive plug includes dopedpolycrystalline silicon or a refractory metal.

In yet another embodiment of the first aspect, the electronic devicefurther includes a source region lying adjacent to the primary surface,and a well region lying adjacent to the primary surface, wherein aportion of the well region is a channel region for the transistor andlies between the source region and he horizontally-oriented dopedregion. In a particular embodiment, the electronic device furtherincludes a well contact region lying adjacent to the source region, anan interconnect contacting the source region and the well contactregion. In a more particular embodiment, the electronic device isconfigured such that when the electronic device would be in a normaloperating state, a principal charge carrier flow is from the sourceregion to the underlying doped region via the well region,horizontally-oriented doped region, and the vertically-orientedconductive structure. In another particular embodiment, the electronicdevice further includes a gate electrode overlying portions of thesource region and the channel region. In a further embodiment, aninterconnect does not overlie and contact the horizontally-orienteddoped region or the vertically-oriented conductive region.

In a second aspect, an electronic device can include a semiconductorlayer having a primary surface and a conductive structure. Theconductive structure can include a horizontally-oriented doped regionlying adjacent to the primary surface, wherein a portion of the wellregion lies between the source region and the horizontally-orienteddoped region, an underlying doped region spaced apart from the primarysurface, and a vertically-oriented conductive region lying between thedoped horizontal region and the underlying doped region. Thesemiconductor device can also include a source region lying adjacent tothe primary surface, a well region lying adjacent to the primarysurface, wherein a portion of the well region includes a channel regionthat lies between the source region and the horizontally-oriented dopedregion. The electrode device can further include a gate electrodeoverlying the channel region, and a conductive electrode configured tobe at a substantially constant voltage when the electronic device is ina normal operating state. The conductive electrode can overlie and beelectrically insulated from the conductive structure, and a portion ofthe conductive electrode can lie adjacent to the gate electrode. Theconductive electrode can have a first surface and a second surfaceopposite the first surface, wherein the primary surface is closer to thefirst surface than the second surface. Within an area occupied by thetransistor, each of the first and second surfaces of the conductiveelectrode can lie at elevations between lowermost and uppermost pointsof the gate electrode.

In embodiment of the second aspect, the electronic device can furtherinclude a gate signal line overlying the primary surface of thesemiconductor layer and the conductive structure, wherein within thetransistor the gate signal line overlies the conductive electrode. In afurther embodiment, the horizontally-oriented doped region extendsapproximately 0.2 to 2.0 microns along the primary surface from thevertically-oriented conductive region toward the source region. Inanother embodiment, the semiconductor layer has a thickness no greaterthan approximately 5 microns, a portion of the semiconductor layer liesoutside of the well region, the source region, the horizontally-orienteddoped region, and the vertically-oriented conductive region, and theportion of the semiconductor layer has a dopant concentration of nogreater than approximately 1×10¹⁶ atoms/cm³. In a particular embodiment,the dopant concentration is no greater than approximately 1×10¹⁵atoms/cm³. In another particular embodiment, the portion of thesemiconductor layer, the source region, the horizontally-oriented dopedregion, and the underlying doped region have a same conductivity type.

In a further particular embodiment of the second aspect, the portion ofthe semiconductor layer and the well region have a first conductivitytype, and the source region, the horizontally-oriented doped region, andthe underlying doped region has a second conductivity type opposite thefirst conductivity type. In yet a further particular embodiment, thehorizontally-oriented doped region has a peak dopant concentration of atleast approximately 2×10¹⁷ atoms/cm³, and each of thevertically-oriented conductive region and the underlying doped regionhas a peak dopant concentration of at least approximately 1×10¹⁹atoms/cm³. In a more particular embodiment, the peak dopantconcentration of the horizontally-oriented doped region is no greaterthan approximately 2×10¹⁸ atoms/cm³.

In still another embodiment of the second aspect, an interconnect doesnot overlie and contact the horizontally-oriented doped region or thevertically-oriented conductive region.

In a third aspect, an electronic device can include a field-effecttransistor including a gate dielectric layer. The field-effecttransistor can be designed to have a maximum gate voltage ofapproximately 20 V, a maximum drain voltage of approximately 30 V, and afigure of merit no greater than approximately 30 mΩ*nC.

In an embodiment of the third aspect, the figure of merit is no greaterthan 20 mΩ*nC. In another embodiment, the field-effect transistor isdesigned to have a switching speed of at least approximately 2 MHz. Instill another embodiment, the field-effect transistor further includes achannel region that principally includes a Group 14 element.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed is not necessarily the order inwhich they are performed.

Certain features are, for clarity, described herein in the context ofseparate embodiments, may also be provided in combination in a singleembodiment. Conversely, various features that are for brevity, describedin the context of a single embodiment, may also be provided separatelyor in any subcombination. Further, reference to values stated in rangesincludes each and every value within that range.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

The specification and illustrations of the embodiments described hereinare intended to provide a general understanding of the structure of thevarious embodiments. The specification and illustrations are notintended to serve as an exhaustive and comprehensive description of allof the elements and features of apparatus and systems that use thestructures or methods described herein. Separate embodiments may also beprovided in combination in a single embodiment, and conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.Further, reference to values stated in ranges includes each and everyvalue within that range. Many other embodiments may be apparent toskilled artisans only after reading this specification. Otherembodiments may be used and derived from the disclosure, such that astructural substitution, logical substitution, or another change may bemade without departing from the scope of the disclosure. Accordingly,the disclosure is to be regarded as illustrative rather thanrestrictive.

1. An electronic device comprising a transistor, wherein the transistorcomprises: a semiconductor layer having a primary surface; a conductivestructure comprising: a horizontally-oriented doped region lyingadjacent to the primary surface; an underlying doped region spaced apartfrom the primary surface and the horizontally-oriented doped region; anda vertically-oriented conductive region extending through a majority ofthe thickness of the semiconductor layer and electrically connecting thedoped horizontal region and the underlying doped region; a conductiveelectrode overlying and electrically insulated from the conductivestructure, wherein the conductive electrode is configured to be at asubstantially constant voltage when the electronic device is in a normaloperating state; a gate electrode overlying the primary surface of thesemiconductor layer; and a gate signal line overlying the primarysurface of the semiconductor layer and the conductive structure, whereinwithin an area occupied by the transistor, the gate signal line overliesthe conductive electrode.
 2. The electronic device of claim 1, whereinthe vertically-oriented conductive region comprises an elevated portionthat overlies the primary surface of the semiconductor layer.
 3. Theelectronic device of claim 2, wherein the elevated portion has anuppermost surface that lies at an elevation higher than a lowermostsurface of the gate electrode.
 4. The electronic device of claim 1,wherein: the semiconductor layer comprises a compensating region; thecompensating region lies between the horizontally-oriented doped regionand the underlying doped region and extends substantially to thevertically-oriented conductive region; and the compensating region hasconductivity type opposite that of the horizontally-oriented dopedregion and the underlying doped region.
 5. The electronic device ofclaim 1, wherein the vertically-oriented conductive structure comprisesa conductive plug.
 6. The electronic device of claim 5, wherein theconductive plug comprises doped polycrystalline silicon.
 7. Theelectronic device of claim 5, wherein the conductive plug comprises arefractory metal.
 8. The electronic device of the claim 1, furthercomprising: a source region lying adjacent to the primary surface; and awell region lying adjacent to the primary surface, wherein a portion ofthe well region is a channel region for the transistor and lies betweenthe source region and the horizontally-oriented doped region.
 9. Theelectronic device of claim 8, further comprising: a well contact regionlying adjacent to the source region; and an interconnect contacting thesource region and the well contact region.
 10. The electronic device ofclaim 9, wherein the electronic device is configured such that when theelectronic device would be in a normal operating state, a principalcharge carrier flow is from the source region to the underlying dopedregion via the well region, horizontally-oriented doped region, and thevertically-oriented conductive structure.
 11. The electronic device ofclaim 8, further comprising a gate electrode overlying portions of thesource region and the channel region.
 12. The electronic device of claim1, wherein an interconnect does not overlie and contact thehorizontally-oriented doped region or the vertically-oriented conductiveregion.
 13. An electronic device comprising, a semiconductor layerhaving a primary surface; a conductive structure comprising: ahorizontally-oriented doped region lying adjacent to the primarysurface, wherein a portion of the well region lies between the sourceregion and the horizontally-oriented doped region; an underlying dopedregion spaced apart from the primary surface; and a vertically-orientedconductive region lying between the doped horizontal region and theunderlying doped region; a source region lying adjacent to the primarysurface; a well region lying adjacent to the primary surface, wherein aportion of the well region includes a channel region that lies betweenthe source region and the horizontally-oriented doped region; a gateelectrode overlying the channel region; and a conductive electrodeconfigured to be at a substantially constant voltage when the electronicdevice is in a normal operating state, wherein: the conductive electrodeoverlies and is electrically insulated from the conductive structure; aportion of the conductive electrode lies adjacent to the gate electrode;the conductive electrode has a first surface and a second surfaceopposite the first surface; the primary surface is closer to the firstsurface tan the second surface; and within an area occupied by thetransistor, each of the first and second surfaces of the conductiveelectrode lies at elevations between lowermost and uppermost points ofthe gate electrode.
 14. The electronic device of claim 13 furthercomprising a gate signal line overlying the primary surface of thesemiconductor layer and the conductive structure, wherein within thetransistor, the gate signal line overlies the conductive electrode. 15.The electronic device of claim 13, wherein the horizontally-orienteddoped region extends approximately 0.2 to 2.0 microns along the primarysurface from the vertically-oriented conductive region toward the sourceregion.
 16. The electronic device of claim 14, wherein: thesemiconductor layer has a thickness no greater than approximately 5microns; a portion of the semiconductor layer lies outside of the wellregion, the source region, the horizontally-oriented doped region, andthe vertically-oriented conductive region; and the portion of thesemiconductor layer has a dopant concentration of no greater thanapproximately 1×10¹⁶ atoms/cm³.
 17. The electronic device of claim 16,wherein the dopant concentration is no greater than approximately 1×10¹⁵atoms/cm³.
 18. The electronic device of claim 16, wherein the portion ofthe semiconductor layer, the source region, the horizontally-orienteddoped region, and the underlying doped region have a same conductivitytype.
 19. The electronic device of claim 16, wherein: the potion of thesemiconductor layer and the well region have a first conductivity type;and the source region, the horizontally-oriented doped region, and theunderlying doped region has a second conductivity type opposite thefirst conductivity type.
 20. The electronic device of claim 16, wherein:the horizontally-oriented doped region has a peak dopant concentrationof at least approximately 2×10¹⁷ atoms/cm³; and each of thevertically-oriented conductive region and the underlying doped regionhas a peak dopant concentration of at least approximately 1×10¹⁹atoms/cm³.
 21. The electronic device of claim 20, wherein the peakdopant concentration of the horizontally-oriented doped region is nogreater than approximately 2×10¹⁸ atoms/cm³.
 22. The electronic deviceof claim 13, wherein an interconnect does not overlie and contact thehorizontally-oriented doped region or the vertically-oriented conductiveregion.
 23. An electronic device comprising a field-effect transistorcomprising a gate dielectric layer, wherein the field-effect transistoris designed to have a maximum gate voltage of approximately 20 V, amaximum drain voltage of approximately 30 V, and a figure of merit nogreater than approximately 30 mΩ*nC.
 24. The electronic device of claim23, wherein the figure of merit is no greater than 20 mΩ*nC.
 25. Theelectronic device of claim 23, wherein the field-effect transistor isdesigned to have a switching speed of at least approximately 2 MHz. 26.The electronic device of claim 23, wherein the field-effect transistorfurther comprises a channel region that principally comprises a Group 14element.